Pre-filled cartridges with a liquid drug are well known in connection with drug delivery devices to deliver the liquid drug by means of an injection needle with a distal needle tip adapted to penetrate tissue. To prevent a negative impact on the liquid drug during storage, yet to ease the preparation of an injection, it is known from the state of the art to seal pre-filled cartridges with a septum that is penetrated by a proximal needle tip of the injection needle immediately before the injection. Also, caps for covering at least the distal needle tip of an injection needle in order to prevent accidental needle sticks are known for such drug delivery devices. According to the state of the art, a user removes the cap and loads a pre-filled cartridge into the drug delivery device such that the proximal needle tip of the injection needle pierces through the septum of the pre-filled cartridge in order to prepare an injection.